I suspect this will get more traction.
Google just announced that they're going to start charging their GSuite legacy users (includes email). My current plan allows 25 users with e-mail (and Drive and other associated Google services) for free.
Naturally, once I heard the news, I started to investigate what my options were. Truth be told, I was contemplating moving away from Google prior to this due to their creepy nature.
I have 4 members in my Family Sharing group, but 3 others who use my domain but aren't part of my group (my sisters and father - they can pay for their own stuff, thanks). I'd like to at least forward their e-mail to whatever they choose to replace Gmail with (or still to a Gmail address), but it appears I cannot.
Apple should allow the forwarding of other "non-Family Sharing" users to other e-mail addresses (like Gmail or Outlook or whatever).
Otherwise, my domain is limited to just 6 users for e-mail if I move it over.